On Wednesday, Forbes released its annual list of highest-paid actors and, for the first time, Robert Downey Jr. topped the list. The man best known these days for playing Tony Stark had raked in $75 million between June 2012 and June of this year, best among all actors.

News reports were breathless -- not least of which the report from Forbes itself, which touted his success as a coup of sorts. “It’s hard to remember that just a few years ago, Downey was box office poison, and regarded by the studios as damaged goods.” Now, the magazine said, “he’s a hit machine.”

Well, Marvel is the hit machine -- Downey has struggled outside it -- but that’s a separate post. But there’s a bigger point in the Downey crowning: though he may be earning more than ever, he’s not necessarily doing his best work.

Even ardent Downey fans would be hard-pressed to call his two movies over the highest-paid period superlative, or enduring. “Iron Man 3” is derivative stuff -- derivative of himself, sure, but still hardly fresh. And while as a movie “The Avengers” had its virtues, 'Tony Stark redux' was not high on the list. That’s not to say Downey isn’t still a good actor. It’s just that his best stuff came well before he started making top bank.

What’s interesting is that when you look at past holders of the Forbes title, Downey is hardly an exception. The list is filled with strong performers who did their best work years or even decades before they drove the biggest Brinks truck. Last year it was Tom Cruise who topped Forbes' list. Cruise has made some great movies over the last three decades: “Top Gun,” “Rain Man,” the first “Mission: Impossible,” “Minority Report” even “Tropic Thunder.” There’s a reason why studios would pay him big bucks.

Unfortunately, what he made during the June 2011 to June 2012 period wasn't close to these movies: “Mission Impossible: Ghost Protocol” and “Rock of Ages.” And he was about to enter a period when he would make several other films that could hardly be called Oscar gems: “Jack Reacher” and “Oblivion.”

The trend follows down the line: a 2011-era Leonardo DiCaprio, a circa-2010 Johnny Depp. The most glaring example in recent years may have come in 2009, when Harrison Ford landed the honor. Ford climbed to the top of the list courtesy of his payout in “Indiana Jones and the Kingdom of the Crystal Skull," a movie whose most notable achievement is that it paid Harrison Ford that much money to star in "Indiana Jones and the Kingdom of the Crystal Skull."

The problem with the money metric is that, with just a few exceptions, by the time the actors are getting the big bucks, they’ve already long finished with their great work and are now in their payday period. And the biggest paydays these days are for long-in-the-tooth franchises for which studios desperately need the original star, which only exacerbates the problem.

You could argue that landing atop the list is a harbinger of good things to come. After all, once an actor is that financially secure, he should have the freedom to do the kinds of films that best capitalize on his talent, without regard for box office or pocketbook.

But unfortunately it doesn't work that way. Johnny Depp topped the list in 2010. He then took all that moola and freedom it bought and made... "The Tourist," "Pirates of the Caribbean: On Stranger Tides,” “Dark Shadows” and “The Lone Ranger.” “Edward Scissorhands” they weren’t.

It’s all well and good to look at a list like Forbes to determine who studios value at a given moment. But top-earning potential is hardly synonymous with quality. In fact, too often it indicates that the quality has begun to fade.